SimpleQueue

A simple FIFO queue

npm install SimpleQueue

What is this?

There are plenty queues for node, but even those branded as FIFO (first in first out) usually destroy the order. Eg. when mapping over an RSS feeds & doing something with all of the pages, you need to know what element had what position - so I created this little helper.

API

Class: SimpleQueue<T, R>

A simple FIFO queue, delivering items in order.

Type parameters

| Name | Default | Description | | ---- | ------- | ---------------------------------------- | | T | - | Type that is pushed onto the stack. | | R | void | Type that the passed callback maps to. |

Constructors

constructor

+ new SimpleQueue(worker: (element: T, callback: (error: Error | null, result: R) => void) => void, callback: (error: Error | null, result: R, element: T) => void, done?: undefined | () => void, concurrent?: number): SimpleQueue

Defined in index.ts:16

Creates a new FIFO queue.

Parameters:

| Name | Type | Default value | Description | | ------------ | ------------------------------------------------------------------------- | ------------- | ---------------------------------------------------------- | | worker | (element: T, callback: (error: Error | null, result: R) => void) => void | - | Method to call for each child. Args: | | callback | (error: Error | null, result: R, element: T) => void | - | Method to call when an element was processed. | | done? | undefined | () => void | - | Method to call once the stack is cleared. | | concurrent | number | 20 | Number of elements to process in parallel. Defaults to 20. |

Returns: SimpleQueue

Properties

paused

• paused: boolean = false

Defined in index.ts:16

Methods

abort

▸ abort(): void

Defined in index.ts:48

Clears the queue (can't stop running processes).

Returns: void

pause

▸ pause(): void

Defined in index.ts:57

Pause the queue execution. Will not stop already in-flight items.

Returns: void

push

▸ push(props: T): void

Defined in index.ts:41

Adds an element to the queue.

Parameters:

| Name | Type | | ------- | ---- | | props | T |

Returns: void

resume

▸ resume(): void

Defined in index.ts:64

Resume the queue execution, and catch up with remaining items.

Returns: void

Example

import SimpleQueue from "SimpleQueue";

const queue = new SimpleQueue(
    (element, callback) => {
        // Set
        setTimeout(() => callback(null, element / 1000), element);
    },
    (err, result, element) => {
        console.log(result);
    },
    () => {
        console.log("done");
    },
    4
);

queue.push(1000);
queue.push(5000);
queue.push(3000);
queue.push(4000);
queue.push(8000);
queue.push(2000);
queue.push(0);

Output:

1, 5, 3, 4, 8, 2, 0, "done"

This takes 9 seconds to run.